The invention relates to a dust filter which is surrounded by a frame, is held exchangeably in a shaft in an air duct of a heating system or air-conditioning system of a motor vehicle and downstream of which an absorption filter may be arranged.
A filter insert of this type is known from German Patent Document 38 37 968 A1 and fills the entire holding shaft, with the result that, if the motor vehicle is only equipped with a dust filter, this filter insert can migrate axially.
It is an object of the invention to configure a frame which holds a dust filter in such a manner that said frame provides a simple retrofitting means for an exchangeable absorption filter, it being intended, at the same time, to prevent axial migration of the frame when an absorption filter is not being held.
This object is achieved according to preferred embodiments of the invention by providing a filter arrangement which can be exchangeably inserted in a motor vehicle heating or air conditioning system air duct, comprising:
a dust filter assembly composed of a dust filter housed in a dust filter frame, said dust filter frame having an integrally formed frame end section which protrudes beyond the dust filter at an air outlet end of the dust filter, PA1 wherein said frame end section has latching openings for accommodating latching hooks of an absorption filter which can be optionally arranged downstream of the dust filter.
The absorption filter is effectively prevented from bulging, even at high air speeds, if the retaining frame is provided with a grating which is pre-curved resiliently in the direction of the absorption filter to be held, according to especially preferred embodiments of the invention.
The absorption filter is securely held, by gripping along its edge, if the dust filter frame has, on its edge side, an encircling clamping slope as a bearing surface for the absorption filter, according to especially preferred embodiments of the invention.
The gripping action is further increased so that even absorption filters which are in the form of a mat and have a non-rigid construction are retained securely if the frame and the retaining frame have a clamping slope and if this creates an encircling, dovetailed clamping groove for holding the absorption filter, according to especially preferred embodiments of the invention.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.